In December 2016, the company Layer-Großhandels GmbH (Layer) inaugurated a new, modern center for safety engineering at its headquarters in Tettnang. The four-storey building of the wholesale store was constructed in just eight months, using a reinforced concrete skeleton structure. In addition to a generous exhibition space of roughly 700m², it offers plenty of space for offices, training rooms, storage and an apartment on the top floor. The usable floor space is over 2.000m². Highlight: the commercial building is heated and air-conditioned throughout the year without fossil fuels. Deep geothermal probes and concrete core activation make this possible.
 
The wholesale store was built by general contractor Biedenkapp Industriebau GmbH from Wangen. Schneider Gebäudetechnik GmbH was responsible for the building services. The MEP engineering office, founded in 2015, operates with four employees and implements projects in the tri-state area around Lake Constance. In addition to building services, energy management and system optimization are part of their service portfolio. For the Layer project, Schneider has engineered and simulated geothermal energy, heating, ventilation, air conditioning and plumbing system, by applying modern methods of Building Information Modeling (BIM). Tobias Schneider and his team used the Open BIM software DDS-CAD to engineer all MEP systems.

One of Layer's environmental management principles states: „Our sites are engineered and designed with the latest energy-saving processes compliant to German energy certification." A goal of the new building was to dispense with fossil fuels for the heating and air-conditioning of the building. The amendment of the Energy Saving Ordinance (EnEV) has stricter requirements for new buildings since 1 January 2016: the annual primary energy requirement has been reduced by an average of 25 percent. This poses a challenge for MEP engineers, because „the basis for demand-based geothermal energy is a very precise heat load calculation“, explains Tobias Schneider and adds: „No square meter can be missed, no shading can be disregarded for everything to work out fine in the end. Thanks to the intelligent heat load calculation in DDS-CAD, we can now carry out such calculations in a fraction of the usual time. Previously, it took us three to four days to complete a similar heat load calculation. Today we are able perform the calculations in two hours, if we have a proper IFC building model at hand.“

The geothermal energy for Layer is provided via typical double U-tube probes at approximately 180m depth. In the cooling mode the flow/return is at 16/19 °C; in the heating mode it is at 48/33 °C. A special feature is that the system operates with water as a heat transfer medium without the addition of glycol. „With the improved heat capacity compared to a water-glycol mixture, we achieve a 10 percent lower power loss“, emphasizes Schneider. A heating coil protects the only external line, which is merely 1 meter long for connecting the ventilator to the roof, against frost damage. Because of the usable temperature level, the cooling runs without heat pump operation. This saves primary energy and is environment friendly, since only electrical energy is needed to operate the circulation pumps. Heat and cold distribution is carried out directly via concrete core activation, underfloor heating and the ventilation system.

„Especially in geothermal energy projects, you have to consider uncontrollable boundary conditions as a MEP engineer“, says Tobias Schneider. „It was only during the drilling that the available geothermal heat output would have been too low for the heat load we had calculated.“ However, the drilling company could increase the heat output by increasing the drill diameters while maintaining the permissible minimum distances between the probes. The rated heat output of geothermal heating is 128 kW.

The seamless data exchange between building owners, architects, and MEP engineers makes or breaks a successful execution of a modern construction process. Hence, Biedenkapp provided virtual 3D building models as IFC files. These were the basis for the interdisciplinary MEP design according to the Open BIM workflow. Subsequently, Schneider handed over his plans to builders and contractors again in IFC and DWG format. From the beginning, an interdisciplinary design of the building services took place in the object-based, intelligent 3D building model.

Schneider says: „Our planning tool, DDS-CAD, is particularly advanced in comparison with other popular programs concerning Open BIM. It is constantly being developed further to optimally support BIM workflows. IFC models can be easily imported into DDS-CAD, and with the help of the 3D building model, we can start engineering immediately.“ He continues: „With other CAD software, you often have to draw from bend to bend and somehow try to create the linking segments. Here I draw as if I lay the pipe itself. This is intuitive and saves time. The software assists you from the start with, for example, interdisciplinary clash prevention.“